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Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, acetal, hemiacetal, tetra-substituted epoxide and a variety of carboxylic esters.
Occurrence and use
Initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria), it is now known to affect over 200 species of insects, by acting mainly as an antifeedant and growth disruptor. It was recently found that azadirachtin possesses considerable toxicity towards African cotton leafworm (Spodoptera littoralis), which are resistant to a commonly used biological pesticide, Bacillus thuringiensis. Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the LD50 in rats is > 3,540 mg/kg making it practically non-toxic).
This compound is found in the seeds (0.2 to 0.8 percent by weight) of the neem tree, Azadirachta indica (hence the prefix aza does not imply an aza compound, but refers to the scientific species name). Many more compounds, related to azadirachtin, are present in the seeds as well as in the leaves and the bark of the neem tree which also show strong biological activities among various pest insects. Effects of these preparations on beneficial arthropods are generally considered to be minimal. Some laboratory and field studies have found neem extracts to be compatible with biological control. Because pure neem oil contains other insecticidal and fungicidal compounds in addition to azadirachtin, it is generally mixed at a rate of 1 US fluid ounce per US gallon (7.8 ml/l) of water when used as a pesticide.
Azadirachtin is the active ingredient in many pesticides including TreeAzin, AzaMax, BioNEEM, AzaGuard, and AzaSol, Terramera Proof and Terramera Cirkil.
Azadirachtin has a synergistic effect with the biocontrol agent Beauveria.
Nimbecidine is a natural product insecticide mix which is mostly azadirachtin, with some other limonoids.